In a conventional matte generator, component signals representative of a luminance component and two color difference components are generated at an operator interface and are applied to a video encoder which also receives horizontal and vertical sync signals and a continuous wave subcarrier reference signal. The encoder might be, for example, a type MC 1377 integrated circuit. The encoder combines the component signals, the sync signals and the subcarrier reference signal to generate a full field baseband video signal representing a solid color. The matte generator may be integrated within a production switcher, or it may be a stand-alone unit. In the production switcher, the matte signal is combined with an external video signal to produce an output video signal. In order for the signals to be combined satisfactorily, it is necessary that the horizontal and vertical timing of the two signals be aligned, and that if the matte signal includes a color burst, the burst of the matte signal be in phase with the burst of the external video signal. In order to adjust the phase of the burst of the matte signal relative to the burst of the second video signal, an adjustable delay network is interposed in the path of the reference subcarrier signal applied to the encoder, and the delay introduced by the delay network is adjusted so that the burst of the matte signal is in phase with the burst of the external video signal.
If multiple matte generators are included in a production switcher and each matte generator generates a matte signal which includes a color burst, it is necessary for the bursts of all the matte signals to be in phase with each other and with the burst of the external video signal. It is very time-consuming and inconvenient to adjust manually the phase of each matte generator.